Identification guide · Metals & Alloys
How to Identify Iron
Iron is usually silver-gray, dark gray, and rust brown with a metallic luster and is opaque. It has a Mohs hardness of 4. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Its streak is gray to dark gray. It is most often confused with Hematite, Aluminum, and Brass; the tests below separate them.
Iron identification checklist
| Color | Silver-gray, Dark gray, Rust brown | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Metallic | Turn it under a lamp: a true metallic shine reflects like polished metal and stays opaque at thin edges. |
| Transparency | Opaque | Hold a thin edge up to a bright light and note whether light passes through. |
| Mohs hardness | 4 | A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. |
| Streak | Gray to dark gray | Drag a corner across unglazed porcelain (the back of a bathroom tile) and check the powder color. |
| Cleavage | None | |
| Fracture | Ductile to uneven | |
| Specific gravity | 7.87 | Very heavy, metallic heft (specific gravity about 7.87). |
Extra tests for Iron
Magnet test. Strongly magnetic.
Iron look-alikes and how to tell them apart
Hematite is harder (Mohs 6) than Iron (Mohs 4), so Hematite will scratch Iron and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Iron vs Hematite →
Iron is harder (Mohs 4) than Aluminum (Mohs 2.75), so Iron will scratch Aluminum and not the other way round. A copper coin (Mohs 3.5) scratches it, but a fingernail does not. Iron vs Aluminum →
Both sit near Mohs 4, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Iron vs Brass →
Iron is harder (Mohs 4) than Bronze (Mohs 3), so Iron will scratch Bronze and not the other way round. A copper coin (Mohs 3.5) scratches it, but a fingernail does not.
Field tips
- Look for gray metal, darkened wear, or orange-brown rust.
- Iron and many iron alloys are magnetic.
- Rust texture can appear powdery, flaky, or rough.
- Common objects include tools, nails, hardware, cookware, and structural parts.
Iron identification FAQ
How can you tell if a rock is Iron?
Check the color (silver-gray, dark gray, and rust brown), the metallic luster, a Mohs hardness of 4 and a gray to dark gray streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Iron?
Iron has a Mohs hardness of 4. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not.
What is the difference between Iron and Hematite?
Iron (Mohs 4, metallic luster) and Hematite (Mohs 6, metallic luster) look alike, but hardness, streak and heft usually separate them. See the full Iron vs Hematite comparison for a side-by-side table.
Is Iron worth anything?
Entry-level Iron specimens sell for around $1, typical collector pieces about $10, and premium examples $100 or more depending on size, quality and locality.
What color is Iron?
Iron is most often silver-gray, dark gray, and rust brown. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
